Method for abrasive cutting in a liquid

ABSTRACT

Materials are immersed in a liquid and then cut by propelling a stream of abrasive particles, which are carried in a fluid, towards the material. The liquid covering the material restricts the stream of abrasive particles to the area to be cut so as to avoid the disadvantage of abrading away the material surface adjacent the cut.

United States Patent Maselli June 10, 1975 [54] METHOD FOR ABRASIVECUTTING IN A 2,955,387 10/1960 Soderman 51/8 R LIQUID 2,985,050 5/1961Schwacha 51/321 X 3,212,378 lO/l965 Rice 5l/32l X [75] inventor:Nicholas F. Maselli, East 3,323,257 6/1967 Fonti 51/8 R Hampstead, N.H.3,524,367 8/1970 Franz 5l/32l X 3 4,972 101972 E 5| 319 [73] Assignee:Western Electric Company, I mels hem-Formed New York N'Y' PrimaryExaminer-Donald G. Kelly [22] Filed: Nov. 16, 1973 Attorney, Agent, orFirmD. J. Kirk [21] Appl. No.: 416,553

[ ABSTRACT 52 us. (:1 51/319; 51/323 Materials are immmed a liquid andcut by 51 Int. Cl. B24c 1/00- B24c 1/04 propelling a Stream of abrasiveParticles whim are 58 Field of Search 51/8 R 51 319-323, carried in afluid towards the material The liquid 5.1326 covering the materialrestricts the stream of abrasive particles to the area to be cut so asto avoid the disad- [56] References Cited vantage of abrading away thematerial surface adja- UNITED STATES PATENTS cent 2,4l9,687 4/1947Luckey 5l/8 R x 9 Claims, 3 Drawing Figures PATENTEDJLIN 10 m5 1:,054

PR/OR ART 1 METHOD FOR ABRASIVE CUTTING IN A LIQUID BACKGROUND OF THEINVENTION 1. Field of the Invention The instant invention relates to amethod for cutting materials. In particular, the invention is directedto abrasive cutting of materials while the materials are covered by aliquid.

2. Description of the Prior Art There are many well-known methods in theprior art directed to severing or cutting materials. These known methodstend to result in the cutting away of too much material, provide roughor uneven cuts, or cause undesirable stresses in the material. Althoughsuch results may be acceptable in certain circumstances, they cannot betolerated in applications where a relatively expensive and sensitivematerial such as quartz crystal is to be severed or cut.

Several well-known methods are presently used for cutting quartz. Onesuch method makes use of a diamond string saw to perform the cuttingoperation. However, diamond string saws are very expensive, cut slowly,require frequent replacement, cause undesirable stresses, and tend tochip the quartz. Such chipping results in deeply penetrating damage andalteration of the crystalline lattice structure of the quartz. Quartzmay also be cut by the use of an air abrasive tool wherein a highvelocity stream of abrasive particles is directed towards the quartz toerode or abrade the material. Although this method has been found to beeffective in substantially eliminating chipping and is faster thancutting by diamond saws, it disadvantageously abrades the surfaceadjacent the cut and results in more material being removed than desireddue to the outward expansion of the stream of abrasive particles oncethey pass through the nozzle of the air abrasive tool. Such surfaceabrading and the excessive removal of quartz has a deleterious affect onthe electromechanical response of quartz crystal in addition to theexpense incurred due to the loss of significant amounts of quartz.

SUMMARY OF THE INVENTION The instant invention solves the foregoingproblems with a method for cutting material by covering the surface ofthe material at the cutting site with a liquid, and propelling a streamof abrasive particles, carried in a fluid under pressure, towards thematerial to cut the material to a predetermined configuration.

This method results in minimal abrasive damage to the surface of thematerial adjacent to the cut and provides substantially parallel edgesat the cut or severed areas which advantageously decreases the loss ofquartz.

These results accrue due to the fact that the abrasive particles arerestricted to a limited path from the nozzle to the material to be cut.The liquid about this path acts as a funnel or a mask which confines anddirects the movement of the particles towards the material to be cut.The velocity of any abrasive particles leaving the restricted path willbe quickly dampened by the surrounding liquid.

Advantageously, by immersing the material to be cut in a liquid any dustor debris generated from the cutting operation remains in the liquid.

An additional advantage is obtained by having the liquid continuouslyflowing to remove the debris caused by the cutting operation. 3

Another advantage is that in cutting piezoelectric material such asquartz the instant method has been found to cause a minimal amount ofstress at the severed or cut sections resulting in a more accurate andreproducible electromechanical response characteristic.

A further advantage is in cutting under a liquid that electrostaticadhesion of abrasive particles to the surface of the material to be cutis precluded.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a prior artabrasive cutting method.

FIG. 2 illustrates the instant inventive abrasive cutting method.

FIG. 3 is an isometric view of an illustrative embodiment of the instantinvention showing a monolithic crystal filter being abrasively severedusing the instant inventive method.

DETAILED DESCRIPTION FIG. 1 shows a prior art abrasivecutting operationwherein a tool nozzle 10 is located proximate an object 11 to be cut orsevered. The nozzle 10 has a restrictive discharge orifice 12 throughwhich an abrasive material 13 carried in a fluid 14 is propelled towardsthe object 11. The propelled fluid 14 expands or flares outwardly fromthe discharge orifice 12 to form a substantially triangularcross-section between the nozzle discharge orifice I2 and the surface 15of the object 11 to be cut or severed. The stream of abrasive material13, carried in fluid 14, is moved across the surface 15 of the object11. A cut defined by walls 21-21, when viewed in crosssection, forms anopening wherein the width of exit 22 is narrower than the width 'ofentrance 23 with the walls having a steepening angle from entrance toexit. This steepening angle from entrance 23 to exit 22 results in arounded shoulder appearance which is caused by both the flaring out ofthe fluid 14 and by a secondary cutting action resulting from theabrasive material 13 in the fluid l4 striking the surface 15 of theobject 11 and rebounding to strike the object again. These reboundingparticles of abrasive material 13 not only cause an undesirableenlargement of the entrance 23 but also disadvantageously abrades thesurface 15 at points remote from the actual cut.

FIG. 2 depicts the same tool nozzle 10 and object 11; however, thesurface of the object to be cut is covered by a liquid 26 whichsurprisingly has been found to substantially limit the aforementionedflaring out and secondary cutting action of the abrasive material 13.The liquid 26 acts as a mask or shield which dampens the secondaryaction of the rebounding particles of abrasive material 13 whilerestricting the abrasive particles to a narrow stream to provide asmaller cut entrance 23 resulting in a cut, when viewed incross-section. having nearly parallel sides. This restriction of thepath of the abrasive material 13 and the dampening action of the liquid26 essentially eliminates the undesirable abrading of the surface 15adjacent to opening 23 and lessens the amount of material removed in thelocale of the cut. The type of liquid 26 which can be used issubstantially unlimited, for a wide variety of liquids such as freon,oil, alcohol, and water have been found to be effective.

Although it is not fully understood why the liquid 26 restricts theflaring of the particles 13, the following theory has been advanced. Thecenter of the stream of particles 13 passing through the nozzle 12 meetwith less resistance and therefore have a higher velocity than thoseparticles at the perimeter of the stream which are adjacent to the innersurface of the nozzle. By introducing the stream of particles 13 into aliquid 26 the outer or lower velocity particles are readily dampened andthe inner or high velocity particles remain and form a near cylindricalstream of particles.

FIG. 3 shows an illustrative embodiment of the instant invention whereina Monolithic Crystal Filter (MCF) 27 is abrasively out under a liquid26, into two sections. Such a MCF 27 is used as a band pass filter. Bycutting the MCF 27 into two sections certain undesirable response modesof the filter are eliminated. The structure and function of the MCF 27is fully described in U.S. Pat. No. 3,564,463 to W. D. Beaver and R. A.Sykes and US. Pat. No. 3,576,506 to R. L. Reynolds and R. A. Sykes.

it should be emphasized that the instant invention is not limited to thecutting of quartz crystal, for a variety of hard or brittle materialssuch as ceramics, aluminum, sheet steel, glass, etc. have been cut usingthe instant method. Any material that can be abrasively cut whilee notin a liquid can be cut under a liquid with attendant advantages hereindescribed.

In the exemplary embodiment of FIG. 3 the MCF 27 is shown seated inrecessed sections 28-28 of supports 29-29 under the surface of theliquid 26 in container 30. The supports 29-29 can be moved in unison, towards and away from the top edge 36 of the container 30 along guiderails 31 under the control of an actuating apparatus 37 whichcommunicates with the supports via a Y-shaped member 38. Nozzle islocated directly above the MCF 27 within container 30 and is mounted formovement transverse to the MCF.

The MCF 27 is comprised of a quartz crystal plate 39 upon which uppermetallic electrodes 41-41, such as gold, are deposited on a firstsurface 42 of the quartz crystal plate and corresponding aligned lowermetallic electrodes 43-43 (indicated by hidden lines) are deposited on asecond surface 44 thereof. The upper metallic electrodes 41-41 areconnected by upper conductors 46-46 to upper terminals 4747 which inturn are terminated on a rectangular shaped ceramic ring 48. The lowermetallic electrodes 43-43 are connected in a similar manner to therectangular shaped ceramic ring 48 via lower conductors 49-49 and lowerterminals 56-56. Upper terminals 4747 and lower terminals 56-56 provideoutput terminations for electrically connecting the MCF 27 when in anoperational circuit while also providing mounting support for thecrystal plate 39 to the ceramic ring 48.

At the start of the cutting operation the nozzle 10 is located to oneside of the MCF 27 and supports 29-29 are in a full upward position,above the surface of the liquid 26. The operator then places the MCF 27in the recessed sections 28- 28 of supports 29-29 which are then loweredinto the liquid 26 under the control of the actuating apparatus 37 andthe Y-shaped member 38. The nozzle 10 is then positioned proximate anedge 57 of the crystal plate 39. The fluid 14 containing the abrasive 13is activated to project the stream of abrasive material through theorifice 12 of nozzle 10 as the nozzle is moved across the first surface42 of the quartz plate 39 causing a cut 58 which severs the quartz plateinto two sections. Once the quartz plate 3') has been severed, theabrasive 13 carrying fluid 14 from the 1ozzle 10 is stopped and thenozzle moved back again to one side of the MCF 27. Supports 29-29 arethen raised to the full upward position, the MCF 27 is removed and a newMCF is placed on the supports and the foregoing steps repeated.

in a particular working model of the exemplary embodiment of the instantinvention the quartz crystal plate 39, having dimensions of l l1/32 X7/16 inches and a thickness of 0.008 inch, was cut using 27 micronaluminum oxide powder as the abrasive 13 with shop air under a pressureof psi as the carrying fluid 14. The MCF 27 was submerged to a depth ofone-fourth inch in water with the nozzle 10, having a round orifice 12of 0.01 1 inches, placed at a distance of 0.015 inch from the quartzcrystal plate 39. The cut was accomplished at a cutting rate of 0.40inch per minute resulting in a clean cut58 with an average entrance orshoulder opening of 0.013 inch and an exit opening of 0.0085 inch in thequartz. Acceptable cuts have been made up to speeds of 0.56 inch perminute.

The aluminum oxide powder used as the abrasive material 13 in the aboveexample may be replaced with any of a variety of abrasive materialsdepending upon the type of cut that would be acceptable. Abrasivematerials 13 such as sand, silicon carbide, boron carbide, carborundumpowder or the like carried in a fluid 14 such as air, nitrogen, alcohol,water, or other gas or liquids under pressures between 20 and psi couldbe used.

As the distance between the orifice 12 and the quartz plate 39 isincreased, the parameters in the working model above remaining the same,the entrance shoulders become more rounded. Where this distance isincreased to 0.025 inch an entrance opening of between 0.019 to 0.20inch and from 0.009 to 0.085 inch at the exit was measured.

It should be realized that the parameters of speed of cut, pressure ofthe propelling fluid 14, orifice 12 size and shape, distance between thenozzle orifice l2 and the material 11 to be cut, and the abrasive 13 tobe used will vary depending on the type and thickness of material 11 tobe cut and steepness required at the walls 21-21 of the cut. However,the important concept, to which the instant invention is directed, isthat the material 11 to be cut or severed be placed under the surface ofthe liquid 26 while directing a stream of abrasive particles 13 thereat.

It is not necessary that any part of the nozzle 10 be immersed in theliquid 26. Cutting may be accomplished with the nozzle orifice 12 abovethe surface of the liquid 26 while the material 11 to be cut is fullyimmersed in the liquid. This may result in uneven cuts but could beacceptable where there are less stringent requirements as to the slopeof the sides 21-21 and the loss of material 11.

It should be realized that in the instant exemplary embodiment the MCF27 can easily be immersed or submerged in the liquid 26. However, whereit is required to cut or sever larger objects such as large sheets ofaluminum or other materials, the liquid 26 could be confined to coverthe surface of the material at the cutting site only.

Although the illustrative embodiment describes the severing of a quartzcrystal plate 39 into two equal size sections, the instant inventiveconcept is not so limited. Clearly, the instant method for abrasivclycutting under a liquid could be used to advantageously cut an unlimitednumber of shapes. slots, holes, or other configurations by the simpleexpedient of causing the nozzle and/or the supporting structure to movealong a predetermined path. Circular and arcuate shaped designs havebeen cut in quartz crystal using the instant method.

By placing the surface of the object H to be cut under a liquid 26, thedust and debris associated with such a cutting operation is confined tothe liquid. In ad dition, the instant embodiment can be arranged in awell-known manner to have the liquid 26 continuously flowing. The liquid26 could then be filtered to remove the debris and reintroduced ordischarged as waste and makeup liquid added. in addition, the liquid 26has been found to substantially preclude any electrostatic adhesion ofabrasive particles 13 to the surface 15 of the material 11 to be cut.

The instant abrasive cutting method, by providing a cut withsubstantially parallel sides, has been found to produce a minimal amountof stress in the cut material 11. This is clearly advantageous whencutting piezoelectric materials where such stresses would affect theelectromechanical response characteristics of the material.

Finally, it should also be clear that a plurality of nozzles 10 used tosimultaneously or sequentially cut materials is clearly feasible basedupon the concepts of this invention.

I claim:

1. A method of forming an aperture in material, comprising the steps of:

covering the surface of the material at a site at which the aperture isto be formed, with a liquid; and

propelling a stream of abrasive particles, carried in a fluid underpressure, against the covered surface of the material to form theaperture in the material.

2. A method of forming an aperture in material, comprising the steps of:

immersing the material in a liquid; and

propelling a stream of abrasive particles, carried in a fluid underpressure, against the immersed surface of the material to form theaperture in the material. 3. An improved method of forming an aperturein material with abrasive particles comprising the step of: propelling astream of abrasive particles, carried in a fluid under pressure, againstthe surface of the material to form the aperture in the material;

wherein the improvement comprises the additional step of:

covering the material in the vicinity of the area wherein the apertureis to be formed, with a liquid,

prior to propelling the stream of abrasive particles,

the liquid restricting the stream of abrasive particles to the areawherein the aperture is to be formed. 4. A method for cutting a quartzcrystal plate having 5 metallic electrodes deposited thereon, comprisingthe steps of:

immersing the crystal plate in a liquid;

positioning a nozzle of an abrasive projecting tool proximate thecrystal plate; and

activating the abrasive projecting tool to project a stream of abrasivematerial towards the immersed crystal plate, cutting the plate.

5. The method for cutting a quartz crystal plate as set forth in claim4, including the additional step of:

immersing the nozzle in the liquid a predetermined distance from thecrystal plate.

6. A method for cutting a monolithic crystal filter plate havingmetallic electrodes thereon, comprising the steps of:

placing the filter plate on supports;

immersing the supports and filter plate in a liquid;

positioning a nozzle of an air abrasive tool proximate the filter plate;

activating the air abrasive tool to project abrasive material towardsthe immersed filter plate; moving the nozzle across the filter plate tosever the plate into two sections;

deactivating the air abrasive tool;

raising the filter plate above the surface of the liquid;

and

removing the severed filter plate.

7. A method of cutting out a desired configuration from material,comprising the steps of:

covering the surface of the material with a liquid;

propelling a stream of abrasive particles, carried in a fluid underpressure, against the covered surface of the material to sever thematerial; and

imparting relative motion between the stream of abrasive particles andthe material to cut out the desired configuration from the material.

8. A method of severing material into sections, comprising the steps of:

covering the surface of the material, at a severing site, with a liquid;and

propelling a stream of abrasive particles, carried in a fluid underpressure, against the covered surface of the material to sever thematerial into sections.

9. A method of forming an aperture in quartz, comprising the steps of:

immersing the quartz in a liquid; and

propelling a stream of abrasive particles, carried in a fluid underpressure, against the immersed surface of the quartz to form theaperture therein. 55 1 l i =1

1. A method of forming an aperture in material, comprising the steps of:covering the surface of the material at a site at which the aperture isto be formed, with a liquid; and propelling a stream of abrasiveparticles, carried in a fluid under pressure, against the coveredsurface of the material to form the aperture in the material.
 2. Amethod of forming an aperture in material, comprising the steps of:immersing the material in a liquid; and propelling a stream of abrasiveparticles, carried in a fluid under pressure, against the immersedsurface of the material to form the aperture in the material.
 3. Animproved method of forming an aperture in material with abrasiveparticles comprising the step of: propelling a stream of abrasiveparticles, carried in a fluid under pressure, against the surface of thematerial to form the aperture in the material; wherein the improvementcomprises the additional step of: covering the material in the vicinityof the area wherein the aperture is to be formed, with a liquid, priorto propelling the stream of abrasive particles, the liquid restrictingthe stream of abrasive particles to the area wherein the aperture is tobe formed.
 4. A method for cutting a quartz crystal plate havingmetallic electrodes deposited thereon, comprising the steps of:immersing the crystal plate in a liquid; positioning a nozzle of anabrasive projecting tool proximate the crystal plate; and activating theabrasive projecting tool to project a stream of abrasive materialtowards the immersed crystal plate, cutting the plate.
 5. The method forcutting a quartz crystal plate as set forth in claim 4, including theadditional step of: immersing the nozzle in the liquid a predetermineddistance from the crystal plate.
 6. A method for cutting a monolithiccrystal filter plate having metallic electrodes thereon, comprising thesteps of: placing the filter plate on supports; immersing the supportsand filter plate in a liquid; positioning a nozzle of an air abrasivetool proximate the filter plate; activating the air abrasive tool toproject abrasive material towards the immersed filter plate; moving thenozzle across the filter plate to sever the plate into two sections;deactivating the air abrasive tool; raising the filter plate above thesurface of the liquid; and removing the severed filter plate.
 7. Amethod of cutting out a desired configuration from material, comprisingthe steps of: covering the surface of the material with a liquid;propelling a stream of abrasive particles, carried in a fluid underpressure, against the covered surface of the material to sever thematerial; and imparting relative motion between the stream of abrasiveparticles and the material to cut out the desired configuration from thematerial.
 8. A method of severing material into sections, comprising thesteps of: covering the surface of the material, at a severing site, witha liquid; and propelling a stream of abrasive particles, carried in afluid under pressure, against the covered surface of the material tosever the material into sections.
 9. A method of forming an aperture inquartz, comprising the steps of: immersing the quartz in a liquid; andpropelling a stream of abrasive particles, carried in a fluid underpressure, against the immersed surface of the quartz to form theaperture therein.